KNOCK-OUT OF K+ CHANNEL IN PITUITARY--PROLACTIN CONTROL AND FEMALE FERTILITY

催乳素(PRL)是一种脑垂体前叶激素，对 女性生育能力。事实上，催乳素的高分泌是主要的 与女性不孕症相关的神经内分泌相关病理。 不幸的是，导致过度分泌的潜在缺陷 PRL的定义仍然不明确。提供一个合理的框架来理解 这些缺陷和治疗相关的病理，是必不可少的 阐明催乳素分泌的细胞和分子机制 监管。正常情况下，催乳素的分泌处于紧张性抑制状态 下丘脑多巴胺(DA)。催乳素的周期性、生理性激增 女性需要从这种多巴胺能抑制中撤退。自.以来 对DA的反应性降低是高催乳素血症的一个标志 症状，我们的注意力集中在细胞和分子基础上 DA对乳酸菌的作用。 我们已经发现并广泛描述了一种内向激活的DA- 正常乳汁中的整流钾通道(K/DA)。K/DA激活 多巴胺导致乳酸膜超极化和停滞 钙依赖动作电位，紧张性催乳素的驱动力 分泌物。体外研究已经证明了这一点的关键作用 D/DA通道在DA调节PRL释放中的作用此外， D/DA的功能表达依赖于雌激素，雌激素可能 解释长期以来公认的雌激素对这个系统的调节作用。在……里面 在这些方面，D/DA通道位于事件层次结构的顶部 多巴胺能调节催乳素分泌。 作为阐明分子基础的第一步 K/DA在乳酸菌中的生理作用，我们克隆了三个不同的 女性垂体前叶组织的K通道基因产物。基于 天然通道和重组通道在功能上的相似性 在非洲爪哇卵母细胞中表达的通道，其中两个基因产物是 编码异源多聚体K/DA的优秀候选亚单位。作为一名 在这些研究的逻辑延伸下，我们建议评估 这个效应器K通道在其生理环境中--整个动物-- 通过转基因技术。为此，我们将设计和建造 “显性-负性”突变体，可抑制野生型K/DA功能 在乳酸菌中。然后我们将创建一个转基因小鼠模型，在这个模型中 该突变体的表达针对脑下垂体促乳素 PRL启动子。这些研究代表着及时而重要的扩展 私家侦探S的作品，并最终将提供对 催乳素分泌紊乱及其对女性生育能力的影响。

Prolactin (PRL), an anterior pituitary hormone, has profound effects on female fertility. In fact, hypersecretion of PRL is the major neuroendocrine-related pathology associated with female infertility. Unfortunately, the underlying defects which lead to the hypersecretion of PRL remain ill-defined. To provide a rational framework for understanding these defects and treating associated pathologies, it is essential to elucidate the cellular and molecular mechanisms of PRL secretion regulation. Normally, PRL secretion is under tonic inhibition by hypothalamic dopamine (DA). Periodic, physiological surges of PRL in females require a withdrawal from this dopaminergic inhibition. Since reduced responsiveness to DA is a hallmark of hyperprolactinemic syndromes, our attention has focused on the cellular and molecular basis of DA action on the lactotrope. We have discovered and extensively characterized a DA-activated inwardly- rectifying potassium channel (K/DA) in normal lactotropes. K/DA activation by DA leads to hyperpolarization of the lactotrope membrane and cessation of calcium-dependent action potentials, the driving force for tonic PRL secretion. In vitro studies have demonstrated a critical role for this D/DA channel in the regulation of PRL release by DA. Furthermore, the functional expression of D/DA is dependent upon estrogen, which may explain a long-recognized modulatory action of estrogen on this system. In these regards, the D/DA channel lies at the top of a hierarchy of events in dopaminergic regulation of PRL secretion. As an initial step in elucidating the molecular basis for the physiological role of K/DA in lactotropes, we have cloned three different K channel gene products from female anterior pituitary tissue. Based on functional similarities between the native channel and recombinant channels expressed in Xenopus oocytes, two of the gene products are excellent candidate subunits encoding a heteromultimeric K/DA. As a logical extension of these studies, we propose to evaluate the role of this effector K channel within its physiological context-the whole animal- through transgenic technology. To this end, we will design and construct "dominant-negative" mutants, capable of inhibiting wild-type K/DA function in lactotropes. We will then create a transgenic mouse model in which expression of this mutant is directed to pituitary lactotropes using the PRL promoter. These studies represent a timely and important extension of the P.I.'s work and will ultimately provide insight into the basis of disorders in PRL secretion and their impact on female fertility.